Conventionally, a device utilizing an oxygen reduction reaction based on electrolysis is developed for use in a dehumidifying device, an oxygen concentration device, a de-oxygenation device, a salt electrolysis device, a gas sensor or a humidity sensor. For an anode of an electrolysis cell for performing the electrolysis, catalyst of platinum, lead, oxides, iridium composite oxide, or ruthenium composite oxide is used while a platinum based catalyst is used for a cathode.
However, for an oxygen reduction reaction, when the voltage applied to a cathode is higher than the theoretical voltage for generating hydrogen, hydrogen is generated at the cathode. For example, when a de-oxygenizing device is used for a refrigerator, a hydrogenation reaction occurs to lower power efficiency. This is due to the fact that Pt has a very high catalytic activity, and therefore easily causes a hydrogenation reaction accompanied with an oxygen reduction reaction. Further, lowering the voltage for electrolysis has a problem that a high electric current cannot be extracted, thus the deoxygenation efficiency is low.